Farm Progress

Cotton may need less nitrogen than you think, depending on the rotation crop.

Ron Smith, Editor

April 9, 2018

2 Min Read
Dan Fromme, left, associate professor, LSU Ag Center, Alexandria, La., discussed cotton and corn production at the Louisiana Agricultural Technology and Management Conference, back in February. With Fromme is Mike Redlich, Bayer CropSciences.

Cotton following corn or soybeans likely needs less nitrogen fertilizer than cotton after cotton—possibly a lot less.

Too much nitrogen fertilizer may hurt yield instead of boost it, says LSU Extension agronomist Dan Fromme, who works out of the LSU AgCenter in Alexandria.

Fromme, speaking at the February Louisiana Technology and Management Conference in Marksville, said several factors affect nitrogen fertilization decisions for cotton, including rotation, irrigation, and soil type.

 Fromme says research data show the detrimental effects of too much nitrogen on cotton. Studies have shown that applying more than the needed nitrogen rate could produce excessive growth and fewer productive structures than cotton that receives recommended rates. Other research shows that nitrogen “in excess of that required for optimum crop performance can reduce yield or fiber quality.”

Studies have also shown that excess nitrogen, especially combined with late-season moisture, may delay maturity, reduce harvest and ginning percentages and promote boll shedding, disease and insect damage.

Preceding crop

The preceding crop makes a big difference, Fromme said. Following a soybean crop, producers should cut nitrogen rate by 10 to 20 pounds per acre. Behind a good winter legume crop, nitrogen rate should be reduced by 30 to 50 pounds.

Related:Corn fostering Bt-resistant worms’ move to cotton

Those lower rates are especially important on fields with a history of excessive stalk growth. Excessive applications and applications made late also contribute to delayed maturity, increased boll rot and tends to make the cotton more attractive to destructive insects.

Fromme recommends adjusting nitrogen rates to soil types as well. For cotton planted dryland on clay, clay loam, silt clay, and silt clay loam soils, recommended nitrogen rate ranges from 90 to 120 pounds. If those soils are irrigated, nitrogen rate adjusts to 100 to 120 pounds per acre.

On lighter soils — fine sandy loam, loamy sand, silt loam and very fine sandy loam — recommendations call for 60 to 90 pounds of nitrogen per acre in dryland and irrigated production.

Fromme says continuing studies indicate that over-fertilization may produce more plant than fiber.

“Cotton that yielded the most was not the tallest and was not the greenest,” he said. “The soil type and the previous crops have an impact on nitrogen rates, and the 2016 and 2017 results validate the LSU nitrogen rate recommendations.”

Fromme showed data from research plots that show cotton following soybeans on some soil types did better with no additional nitrogen. In some cases, adding more nitrogen to cotton that followed soybeans resulted in rank stalks but a lighter boll load.

Related:Cultural practices are key to protecting cotton from disease losses

About the Author(s)

Ron Smith

Editor, Farm Progress

Ron Smith has spent more than 30 years covering Sunbelt agriculture. Ron began his career in agricultural journalism as an Experiment Station and Extension editor at Clemson University, where he earned a Masters Degree in English in 1975. He served as associate editor for Southeast Farm Press from 1978 through 1989. In 1990, Smith helped launch Southern Turf Management Magazine and served as editor. He also helped launch two other regional Turf and Landscape publications and launched and edited Florida Grove and Vegetable Management for the Farm Press Group. Within two years of launch, the turf magazines were well-respected, award-winning publications. Ron has received numerous awards for writing and photography in both agriculture and landscape journalism. He is past president of The Turf and Ornamental Communicators Association and was chosen as the first media representative to the University of Georgia College of Agriculture Advisory Board. He was named Communicator of the Year for the Metropolitan Atlanta Agricultural Communicators Association. Smith also worked in public relations, specializing in media relations for agricultural companies. Ron lives with his wife Pat in Denton, Texas. They have two grown children, Stacey and Nick, and two grandsons, Aaron and Hunter.

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